--
-- Set associative dcache write-through
--
--- TODO (in no specific order):
---
--- * See list in icache.vhdl
--- * Complete load misses on the cycle when WB data comes instead of
--- at the end of line (this requires dealing with requests coming in
--- while not idle...)
--- * Load with update could use one less non-pipelined cycle by moving
--- the register update to the pipeline bubble that exists when going
--- back to the IDLE state.
--
library ieee;
use ieee.std_logic_1164.all;
-- Number of lines in a set
NUM_LINES : positive := 32;
-- Number of ways
- NUM_WAYS : positive := 4
+ NUM_WAYS : positive := 4;
+ -- L1 DTLB entries per set
+ TLB_SET_SIZE : positive := 64;
+ -- L1 DTLB number of sets
+ TLB_NUM_WAYS : positive := 2;
+ -- L1 DTLB log_2(page_size)
+ TLB_LG_PGSZ : positive := 12;
+ -- Non-zero to enable log data collection
+ LOG_LENGTH : natural := 0
);
port (
clk : in std_ulogic;
rst : in std_ulogic;
d_in : in Loadstore1ToDcacheType;
- d_out : out DcacheToWritebackType;
+ d_out : out DcacheToLoadstore1Type;
+
+ m_in : in MmuToDcacheType;
+ m_out : out DcacheToMmuType;
stall_out : out std_ulogic;
wishbone_out : out wishbone_master_out;
- wishbone_in : in wishbone_slave_out
+ wishbone_in : in wishbone_slave_out;
+
+ log_out : out std_ulogic_vector(19 downto 0)
);
end entity dcache;
architecture rtl of dcache is
-- BRAM organisation: We never access more than wishbone_data_bits at
-- a time so to save resources we make the array only that wide, and
- -- use consecutive indices for to make a cache "line"
+ -- use consecutive indices to make a cache "line"
--
-- ROW_SIZE is the width in bytes of the BRAM (based on WB, so 64-bits)
constant ROW_SIZE : natural := wishbone_data_bits / 8;
-- Bit fields counts in the address
+ -- REAL_ADDR_BITS is the number of real address bits that we store
+ constant REAL_ADDR_BITS : positive := 56;
-- ROW_BITS is the number of bits to select a row
constant ROW_BITS : natural := log2(BRAM_ROWS);
-- ROW_LINEBITS is the number of bits to select a row within a line
constant ROW_OFF_BITS : natural := log2(ROW_SIZE);
-- INDEX_BITS is the number if bits to select a cache line
constant INDEX_BITS : natural := log2(NUM_LINES);
+ -- SET_SIZE_BITS is the log base 2 of the set size
+ constant SET_SIZE_BITS : natural := LINE_OFF_BITS + INDEX_BITS;
-- TAG_BITS is the number of bits of the tag part of the address
- constant TAG_BITS : natural := 64 - LINE_OFF_BITS - INDEX_BITS;
+ constant TAG_BITS : natural := REAL_ADDR_BITS - SET_SIZE_BITS;
+ -- TAG_WIDTH is the width in bits of each way of the tag RAM
+ constant TAG_WIDTH : natural := TAG_BITS + 7 - ((TAG_BITS + 7) mod 8);
-- WAY_BITS is the number of bits to select a way
constant WAY_BITS : natural := log2(NUM_WAYS);
-- .. | |- --| ROW_OFF_BITS (3)
-- .. |----- ---| | ROW_BITS (8)
-- .. |-----| | INDEX_BITS (5)
- -- .. --------| | TAG_BITS (53)
+ -- .. --------| | TAG_BITS (45)
subtype row_t is integer range 0 to BRAM_ROWS-1;
subtype index_t is integer range 0 to NUM_LINES-1;
subtype way_t is integer range 0 to NUM_WAYS-1;
+ subtype row_in_line_t is unsigned(ROW_LINEBITS-1 downto 0);
-- The cache data BRAM organized as described above for each way
subtype cache_row_t is std_ulogic_vector(wishbone_data_bits-1 downto 0);
subtype cache_tag_t is std_logic_vector(TAG_BITS-1 downto 0);
-- type cache_tags_set_t is array(way_t) of cache_tag_t;
-- type cache_tags_array_t is array(index_t) of cache_tags_set_t;
- constant TAG_RAM_WIDTH : natural := TAG_BITS * NUM_WAYS;
+ constant TAG_RAM_WIDTH : natural := TAG_WIDTH * NUM_WAYS;
subtype cache_tags_set_t is std_logic_vector(TAG_RAM_WIDTH-1 downto 0);
type cache_tags_array_t is array(index_t) of cache_tags_set_t;
-- The cache valid bits
subtype cache_way_valids_t is std_ulogic_vector(NUM_WAYS-1 downto 0);
type cache_valids_t is array(index_t) of cache_way_valids_t;
+ type row_per_line_valid_t is array(0 to ROW_PER_LINE - 1) of std_ulogic;
-- Storage. Hopefully "cache_rows" is a BRAM, the rest is LUTs
- signal cache_tags : cache_tags_array_t;
- signal cache_valids : cache_valids_t;
+ signal cache_tags : cache_tags_array_t;
+ signal cache_tag_set : cache_tags_set_t;
+ signal cache_valids : cache_valids_t;
attribute ram_style : string;
attribute ram_style of cache_tags : signal is "distributed";
+ -- L1 TLB.
+ constant TLB_SET_BITS : natural := log2(TLB_SET_SIZE);
+ constant TLB_WAY_BITS : natural := log2(TLB_NUM_WAYS);
+ constant TLB_EA_TAG_BITS : natural := 64 - (TLB_LG_PGSZ + TLB_SET_BITS);
+ constant TLB_TAG_WAY_BITS : natural := TLB_NUM_WAYS * TLB_EA_TAG_BITS;
+ constant TLB_PTE_BITS : natural := 64;
+ constant TLB_PTE_WAY_BITS : natural := TLB_NUM_WAYS * TLB_PTE_BITS;
+
+ subtype tlb_way_t is integer range 0 to TLB_NUM_WAYS - 1;
+ subtype tlb_index_t is integer range 0 to TLB_SET_SIZE - 1;
+ subtype tlb_way_valids_t is std_ulogic_vector(TLB_NUM_WAYS-1 downto 0);
+ type tlb_valids_t is array(tlb_index_t) of tlb_way_valids_t;
+ subtype tlb_tag_t is std_ulogic_vector(TLB_EA_TAG_BITS - 1 downto 0);
+ subtype tlb_way_tags_t is std_ulogic_vector(TLB_TAG_WAY_BITS-1 downto 0);
+ type tlb_tags_t is array(tlb_index_t) of tlb_way_tags_t;
+ subtype tlb_pte_t is std_ulogic_vector(TLB_PTE_BITS - 1 downto 0);
+ subtype tlb_way_ptes_t is std_ulogic_vector(TLB_PTE_WAY_BITS-1 downto 0);
+ type tlb_ptes_t is array(tlb_index_t) of tlb_way_ptes_t;
+ type hit_way_set_t is array(tlb_way_t) of way_t;
+
+ signal dtlb_valids : tlb_valids_t;
+ signal dtlb_tags : tlb_tags_t;
+ signal dtlb_ptes : tlb_ptes_t;
+ attribute ram_style of dtlb_tags : signal is "distributed";
+ attribute ram_style of dtlb_ptes : signal is "distributed";
+
+ -- Record for storing permission, attribute, etc. bits from a PTE
+ type perm_attr_t is record
+ reference : std_ulogic;
+ changed : std_ulogic;
+ nocache : std_ulogic;
+ priv : std_ulogic;
+ rd_perm : std_ulogic;
+ wr_perm : std_ulogic;
+ end record;
+
+ function extract_perm_attr(pte : std_ulogic_vector(TLB_PTE_BITS - 1 downto 0)) return perm_attr_t is
+ variable pa : perm_attr_t;
+ begin
+ pa.reference := pte(8);
+ pa.changed := pte(7);
+ pa.nocache := pte(5);
+ pa.priv := pte(3);
+ pa.rd_perm := pte(2);
+ pa.wr_perm := pte(1);
+ return pa;
+ end;
+
+ constant real_mode_perm_attr : perm_attr_t := (nocache => '0', others => '1');
+
-- Type of operation on a "valid" input
type op_t is (OP_NONE,
+ OP_BAD, -- NC cache hit, TLB miss, prot/RC failure
+ OP_STCX_FAIL, -- conditional store w/o reservation
OP_LOAD_HIT, -- Cache hit on load
OP_LOAD_MISS, -- Load missing cache
OP_LOAD_NC, -- Non-cachable load
- OP_BAD, -- BAD: Cache hit on NC load/store
OP_STORE_HIT, -- Store hitting cache
OP_STORE_MISS); -- Store missing cache
-- Cache state machine
type state_t is (IDLE, -- Normal load hit processing
- LOAD_UPDATE, -- Load with update extra cycle
- LOAD_UPDATE2, -- Load with update extra cycle
RELOAD_WAIT_ACK, -- Cache reload wait ack
STORE_WAIT_ACK, -- Store wait ack
NC_LOAD_WAIT_ACK);-- Non-cachable load wait ack
-- which means that the BRAM output is delayed by an extra cycle.
--
-- Thus, the dcache has a 2-stage internal pipeline for cache hits
- -- with no stalls.
+ -- with no stalls. Stores also complete in 2 cycles in most
+ -- circumstances.
+ --
+ -- A request proceeds through the pipeline as follows.
--
- -- All other operations are handled via stalling in the first stage.
+ -- Cycle 0: Request is received from loadstore or mmu if either
+ -- d_in.valid or m_in.valid is 1 (not both). In this cycle portions
+ -- of the address are presented to the TLB tag RAM and data RAM
+ -- and the cache tag RAM and data RAM.
--
- -- The second stage can thus complete a hit at the same time as the
- -- first stage emits a stall for a complex op.
+ -- Clock edge between cycle 0 and cycle 1:
+ -- Request is stored in r0 (assuming r0_full was 0). TLB tag and
+ -- data RAMs are read, and the cache tag RAM is read. (Cache data
+ -- comes out a cycle later due to its output register, giving the
+ -- whole of cycle 1 to read the cache data RAM.)
--
+ -- Cycle 1: TLB and cache tag matching is done, the real address
+ -- (RA) for the access is calculated, and the type of operation is
+ -- determined (the OP_* values above). This gives the TLB way for
+ -- a TLB hit, and the cache way for a hit or the way to replace
+ -- for a load miss.
+ --
+ -- Clock edge between cycle 1 and cycle 2:
+ -- Request is stored in r1 (assuming r1.full was 0)
+ -- The state machine transitions out of IDLE state for a load miss,
+ -- a store, a dcbz, or a non-cacheable load. r1.full is set to 1
+ -- for a load miss, dcbz or non-cacheable load but not a store.
+ --
+ -- Cycle 2: Completion signals are asserted for a load hit,
+ -- a store (excluding dcbz), a TLB operation, a conditional
+ -- store which failed due to no matching reservation, or an error
+ -- (cache hit on non-cacheable operation, TLB miss, or protection
+ -- fault).
+ --
+ -- For a load miss, store, or dcbz, the state machine initiates
+ -- a wishbone cycle, which takes at least 2 cycles. For a store,
+ -- if another store comes in with the same cache tag (therefore
+ -- in the same 4k page), it can be added on to the existing cycle,
+ -- subject to some constraints.
+ -- While r1.full = 1, no new requests can go from r0 to r1, but
+ -- requests can come in to r0 and be satisfied if they are
+ -- cacheable load hits or stores with the same cache tag.
+ --
+ -- Writing to the cache data RAM is done at the clock edge
+ -- at the end of cycle 2 for a store hit (excluding dcbz).
+ -- Stores that miss are not written to the cache data RAM
+ -- but just stored through to memory.
+ -- Dcbz is done like a cache miss, but the wishbone cycle
+ -- is a write rather than a read, and zeroes are written to
+ -- the cache data RAM. Thus dcbz will allocate the line in
+ -- the cache as well as zeroing memory.
+ --
+ -- Since stores are written to the cache data RAM at the end of
+ -- cycle 2, and loads can come in and hit on the data just stored,
+ -- there is a two-stage bypass from store data to load data to
+ -- make sure that loads always see previously-stored data even
+ -- if it has not yet made it to the cache data RAM.
+ --
+ -- Load misses read the requested dword of the cache line first in
+ -- the memory read request and then cycle around through the other
+ -- dwords. The load is completed on the cycle after the requested
+ -- dword comes back from memory (using a forwarding path, rather
+ -- than going via the cache data RAM). We maintain an array of
+ -- valid bits per dword for the line being refilled so that
+ -- subsequent load requests to the same line can be completed as
+ -- soon as the necessary data comes in from memory, without
+ -- waiting for the whole line to be read.
+
+ -- Stage 0 register, basically contains just the latched request
+ type reg_stage_0_t is record
+ req : Loadstore1ToDcacheType;
+ tlbie : std_ulogic; -- indicates a tlbie request (from MMU)
+ doall : std_ulogic; -- with tlbie, indicates flush whole TLB
+ tlbld : std_ulogic; -- indicates a TLB load request (from MMU)
+ mmu_req : std_ulogic; -- indicates source of request
+ d_valid : std_ulogic; -- indicates req.data is valid now
+ end record;
+
+ signal r0 : reg_stage_0_t;
+ signal r0_full : std_ulogic;
+
+ type mem_access_request_t is record
+ op : op_t;
+ valid : std_ulogic;
+ dcbz : std_ulogic;
+ real_addr : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+ data : std_ulogic_vector(63 downto 0);
+ byte_sel : std_ulogic_vector(7 downto 0);
+ hit_way : way_t;
+ same_tag : std_ulogic;
+ mmu_req : std_ulogic;
+ end record;
-- First stage register, contains state for stage 1 of load hits
-- and for the state machine used by all other operations
--
type reg_stage_1_t is record
- -- Latch the complete request from ls1
- req : Loadstore1ToDcacheType;
+ -- Info about the request
+ full : std_ulogic; -- have uncompleted request
+ mmu_req : std_ulogic; -- request is from MMU
+ req : mem_access_request_t;
-- Cache hit state
hit_way : way_t;
hit_load_valid : std_ulogic;
-
- -- Register update (load/store with update)
- update_valid : std_ulogic;
-
- -- Data buffer for "slow" read ops (load miss and NC loads).
- slow_data : std_ulogic_vector(63 downto 0);
- slow_valid : std_ulogic;
+ hit_index : index_t;
+ cache_hit : std_ulogic;
+
+ -- TLB hit state
+ tlb_hit : std_ulogic;
+ tlb_hit_way : tlb_way_t;
+ tlb_hit_index : tlb_index_t;
+
+ -- 2-stage data buffer for data forwarded from writes to reads
+ forward_data1 : std_ulogic_vector(63 downto 0);
+ forward_data2 : std_ulogic_vector(63 downto 0);
+ forward_sel1 : std_ulogic_vector(7 downto 0);
+ forward_valid1 : std_ulogic;
+ forward_way1 : way_t;
+ forward_row1 : row_t;
+ use_forward1 : std_ulogic;
+ forward_sel : std_ulogic_vector(7 downto 0);
-- Cache miss state (reload state machine)
state : state_t;
+ dcbz : std_ulogic;
+ write_bram : std_ulogic;
+ write_tag : std_ulogic;
+ slow_valid : std_ulogic;
wb : wishbone_master_out;
+ reload_tag : cache_tag_t;
store_way : way_t;
store_row : row_t;
store_index : index_t;
+ end_row_ix : row_in_line_t;
+ rows_valid : row_per_line_valid_t;
+ acks_pending : unsigned(2 downto 0);
+ inc_acks : std_ulogic;
+ dec_acks : std_ulogic;
+
+ -- Signals to complete (possibly with error)
+ ls_valid : std_ulogic;
+ ls_error : std_ulogic;
+ mmu_done : std_ulogic;
+ mmu_error : std_ulogic;
+ cache_paradox : std_ulogic;
+
+ -- Signal to complete a failed stcx.
+ stcx_fail : std_ulogic;
end record;
signal r1 : reg_stage_1_t;
- -- Second stage register, only used for load hits
+ -- Reservation information
--
- type reg_stage_2_t is record
- hit_way : way_t;
- hit_load_valid : std_ulogic;
- load_is_update : std_ulogic;
- load_reg : std_ulogic_vector(4 downto 0);
- data_shift : std_ulogic_vector(2 downto 0);
- length : std_ulogic_vector(3 downto 0);
- sign_extend : std_ulogic;
- byte_reverse : std_ulogic;
- xerc : xer_common_t;
+ type reservation_t is record
+ valid : std_ulogic;
+ addr : std_ulogic_vector(63 downto LINE_OFF_BITS);
end record;
- signal r2 : reg_stage_2_t;
+ signal reservation : reservation_t;
-- Async signals on incoming request
signal req_index : index_t;
signal req_hit_way : way_t;
signal req_tag : cache_tag_t;
signal req_op : op_t;
- signal req_laddr : std_ulogic_vector(63 downto 0);
+ signal req_data : std_ulogic_vector(63 downto 0);
+ signal req_same_tag : std_ulogic;
+ signal req_go : std_ulogic;
+
+ signal early_req_row : row_t;
+
+ signal cancel_store : std_ulogic;
+ signal set_rsrv : std_ulogic;
+ signal clear_rsrv : std_ulogic;
+
+ signal r0_valid : std_ulogic;
+ signal r0_stall : std_ulogic;
+
+ signal use_forward1_next : std_ulogic;
+ signal use_forward2_next : std_ulogic;
-- Cache RAM interface
type cache_ram_out_t is array(way_t) of cache_row_t;
signal replace_way : way_t;
-- Wishbone read/write/cache write formatting signals
- signal bus_sel : wishbone_sel_type;
- signal store_data : wishbone_data_type;
-
+ signal bus_sel : std_ulogic_vector(7 downto 0);
+
+ -- TLB signals
+ signal tlb_tag_way : tlb_way_tags_t;
+ signal tlb_pte_way : tlb_way_ptes_t;
+ signal tlb_valid_way : tlb_way_valids_t;
+ signal tlb_req_index : tlb_index_t;
+ signal tlb_hit : std_ulogic;
+ signal tlb_hit_way : tlb_way_t;
+ signal pte : tlb_pte_t;
+ signal ra : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+ signal valid_ra : std_ulogic;
+ signal perm_attr : perm_attr_t;
+ signal rc_ok : std_ulogic;
+ signal perm_ok : std_ulogic;
+ signal access_ok : std_ulogic;
+
+ -- TLB PLRU output interface
+ type tlb_plru_out_t is array(tlb_index_t) of std_ulogic_vector(TLB_WAY_BITS-1 downto 0);
+ signal tlb_plru_victim : tlb_plru_out_t;
+
--
-- Helper functions to decode incoming requests
--
-- Return the cache line index (tag index) for an address
- function get_index(addr: std_ulogic_vector(63 downto 0)) return index_t is
+ function get_index(addr: std_ulogic_vector) return index_t is
begin
- return to_integer(unsigned(addr(63-TAG_BITS downto LINE_OFF_BITS)));
+ return to_integer(unsigned(addr(SET_SIZE_BITS - 1 downto LINE_OFF_BITS)));
end;
-- Return the cache row index (data memory) for an address
- function get_row(addr: std_ulogic_vector(63 downto 0)) return row_t is
+ function get_row(addr: std_ulogic_vector) return row_t is
+ begin
+ return to_integer(unsigned(addr(SET_SIZE_BITS - 1 downto ROW_OFF_BITS)));
+ end;
+
+ -- Return the index of a row within a line
+ function get_row_of_line(row: row_t) return row_in_line_t is
+ variable row_v : unsigned(ROW_BITS-1 downto 0);
begin
- return to_integer(unsigned(addr(63-TAG_BITS downto ROW_OFF_BITS)));
+ row_v := to_unsigned(row, ROW_BITS);
+ return row_v(ROW_LINEBITS-1 downto 0);
end;
-- Returns whether this is the last row of a line
- function is_last_row_addr(addr: wishbone_addr_type) return boolean is
- constant ones : std_ulogic_vector(ROW_LINEBITS-1 downto 0) := (others => '1');
+ function is_last_row_addr(addr: wishbone_addr_type; last: row_in_line_t) return boolean is
begin
- return addr(LINE_OFF_BITS-1 downto ROW_OFF_BITS) = ones;
+ return unsigned(addr(LINE_OFF_BITS-1 downto ROW_OFF_BITS)) = last;
end;
-- Returns whether this is the last row of a line
- function is_last_row(row: row_t) return boolean is
- variable row_v : std_ulogic_vector(ROW_BITS-1 downto 0);
- constant ones : std_ulogic_vector(ROW_LINEBITS-1 downto 0) := (others => '1');
+ function is_last_row(row: row_t; last: row_in_line_t) return boolean is
begin
- row_v := std_ulogic_vector(to_unsigned(row, ROW_BITS));
- return row_v(ROW_LINEBITS-1 downto 0) = ones;
+ return get_row_of_line(row) = last;
end;
-- Return the address of the next row in the current cache line
end;
-- Get the tag value from the address
- function get_tag(addr: std_ulogic_vector(63 downto 0)) return cache_tag_t is
+ function get_tag(addr: std_ulogic_vector) return cache_tag_t is
begin
- return addr(63 downto 64-TAG_BITS);
+ return addr(REAL_ADDR_BITS - 1 downto SET_SIZE_BITS);
end;
-- Read a tag from a tag memory row
function read_tag(way: way_t; tagset: cache_tags_set_t) return cache_tag_t is
begin
- return tagset((way+1) * TAG_BITS - 1 downto way * TAG_BITS);
+ return tagset(way * TAG_WIDTH + TAG_BITS - 1 downto way * TAG_WIDTH);
end;
- -- Write a tag to tag memory row
- procedure write_tag(way: in way_t; tagset: inout cache_tags_set_t;
- tag: cache_tag_t) is
+ -- Read a TLB tag from a TLB tag memory row
+ function read_tlb_tag(way: tlb_way_t; tags: tlb_way_tags_t) return tlb_tag_t is
+ variable j : integer;
begin
- tagset((way+1) * TAG_BITS - 1 downto way * TAG_BITS) := tag;
+ j := way * TLB_EA_TAG_BITS;
+ return tags(j + TLB_EA_TAG_BITS - 1 downto j);
end;
- -- Generate byte enables from sizes
- function length_to_sel(length : in std_logic_vector(3 downto 0)) return std_ulogic_vector is
+ -- Write a TLB tag to a TLB tag memory row
+ procedure write_tlb_tag(way: tlb_way_t; tags: inout tlb_way_tags_t;
+ tag: tlb_tag_t) is
+ variable j : integer;
begin
- case length is
- when "0001" =>
- return "00000001";
- when "0010" =>
- return "00000011";
- when "0100" =>
- return "00001111";
- when "1000" =>
- return "11111111";
- when others =>
- return "00000000";
- end case;
- end function length_to_sel;
-
- -- Calculate shift and byte enables for wishbone
- function wishbone_data_shift(address : in std_ulogic_vector(63 downto 0)) return natural is
+ j := way * TLB_EA_TAG_BITS;
+ tags(j + TLB_EA_TAG_BITS - 1 downto j) := tag;
+ end;
+
+ -- Read a PTE from a TLB PTE memory row
+ function read_tlb_pte(way: tlb_way_t; ptes: tlb_way_ptes_t) return tlb_pte_t is
+ variable j : integer;
begin
- return to_integer(unsigned(address(2 downto 0))) * 8;
- end function wishbone_data_shift;
+ j := way * TLB_PTE_BITS;
+ return ptes(j + TLB_PTE_BITS - 1 downto j);
+ end;
- function wishbone_data_sel(size : in std_logic_vector(3 downto 0);
- address : in std_logic_vector(63 downto 0))
- return std_ulogic_vector is
+ procedure write_tlb_pte(way: tlb_way_t; ptes: inout tlb_way_ptes_t; newpte: tlb_pte_t) is
+ variable j : integer;
begin
- return std_ulogic_vector(shift_left(unsigned(length_to_sel(size)),
- to_integer(unsigned(address(2 downto 0)))));
- end function wishbone_data_sel;
+ j := way * TLB_PTE_BITS;
+ ptes(j + TLB_PTE_BITS - 1 downto j) := newpte;
+ end;
begin
report "geometry bits don't add up" severity FAILURE;
assert (LINE_OFF_BITS = ROW_OFF_BITS + ROW_LINEBITS)
report "geometry bits don't add up" severity FAILURE;
- assert (64 = TAG_BITS + INDEX_BITS + LINE_OFF_BITS)
+ assert (REAL_ADDR_BITS = TAG_BITS + INDEX_BITS + LINE_OFF_BITS)
report "geometry bits don't add up" severity FAILURE;
- assert (64 = TAG_BITS + ROW_BITS + ROW_OFF_BITS)
+ assert (REAL_ADDR_BITS = TAG_BITS + ROW_BITS + ROW_OFF_BITS)
report "geometry bits don't add up" severity FAILURE;
assert (64 = wishbone_data_bits)
report "Can't yet handle a wishbone width that isn't 64-bits" severity FAILURE;
-
+ assert SET_SIZE_BITS <= TLB_LG_PGSZ report "Set indexed by virtual address" severity FAILURE;
+
+ -- Latch the request in r0.req as long as we're not stalling
+ stage_0 : process(clk)
+ variable r : reg_stage_0_t;
+ begin
+ if rising_edge(clk) then
+ assert (d_in.valid and m_in.valid) = '0' report
+ "request collision loadstore vs MMU";
+ if m_in.valid = '1' then
+ r.req.valid := '1';
+ r.req.load := not (m_in.tlbie or m_in.tlbld);
+ r.req.dcbz := '0';
+ r.req.nc := '0';
+ r.req.reserve := '0';
+ r.req.virt_mode := '0';
+ r.req.priv_mode := '1';
+ r.req.addr := m_in.addr;
+ r.req.data := m_in.pte;
+ r.req.byte_sel := (others => '1');
+ r.tlbie := m_in.tlbie;
+ r.doall := m_in.doall;
+ r.tlbld := m_in.tlbld;
+ r.mmu_req := '1';
+ else
+ r.req := d_in;
+ r.req.data := (others => '0');
+ r.tlbie := '0';
+ r.doall := '0';
+ r.tlbld := '0';
+ r.mmu_req := '0';
+ end if;
+ r.d_valid := '0';
+ if rst = '1' then
+ r0_full <= '0';
+ elsif (r1.full = '0' and d_in.hold = '0') or r0_full = '0' then
+ r0 <= r;
+ r0_full <= r.req.valid;
+ end if;
+ -- Sample data the cycle after a request comes in from loadstore1.
+ -- If another request has come in already then the data will get
+ -- put directly into req.data below.
+ if r0.req.valid = '1' and r.req.valid = '0' and r0.d_valid = '0' and
+ r0.mmu_req = '0' then
+ r0.req.data <= d_in.data;
+ r0.d_valid <= '1';
+ end if;
+ end if;
+ end process;
+
+ -- we don't yet handle collisions between loadstore1 requests and MMU requests
+ m_out.stall <= '0';
+
+ -- Hold off the request in r0 when r1 has an uncompleted request
+ r0_stall <= r0_full and (r1.full or d_in.hold);
+ r0_valid <= r0_full and not r1.full and not d_in.hold;
+ stall_out <= r0_stall;
+
+ -- TLB
+ -- Operates in the second cycle on the request latched in r0.req.
+ -- TLB updates write the entry at the end of the second cycle.
+ tlb_read : process(clk)
+ variable index : tlb_index_t;
+ variable addrbits : std_ulogic_vector(TLB_SET_BITS - 1 downto 0);
+ begin
+ if rising_edge(clk) then
+ if m_in.valid = '1' then
+ addrbits := m_in.addr(TLB_LG_PGSZ + TLB_SET_BITS - 1 downto TLB_LG_PGSZ);
+ else
+ addrbits := d_in.addr(TLB_LG_PGSZ + TLB_SET_BITS - 1 downto TLB_LG_PGSZ);
+ end if;
+ index := to_integer(unsigned(addrbits));
+ -- If we have any op and the previous op isn't finished,
+ -- then keep the same output for next cycle.
+ if r0_stall = '0' then
+ tlb_valid_way <= dtlb_valids(index);
+ tlb_tag_way <= dtlb_tags(index);
+ tlb_pte_way <= dtlb_ptes(index);
+ end if;
+ end if;
+ end process;
+
+ -- Generate TLB PLRUs
+ maybe_tlb_plrus: if TLB_NUM_WAYS > 1 generate
+ begin
+ tlb_plrus: for i in 0 to TLB_SET_SIZE - 1 generate
+ -- TLB PLRU interface
+ signal tlb_plru_acc : std_ulogic_vector(TLB_WAY_BITS-1 downto 0);
+ signal tlb_plru_acc_en : std_ulogic;
+ signal tlb_plru_out : std_ulogic_vector(TLB_WAY_BITS-1 downto 0);
+ begin
+ tlb_plru : entity work.plru
+ generic map (
+ BITS => TLB_WAY_BITS
+ )
+ port map (
+ clk => clk,
+ rst => rst,
+ acc => tlb_plru_acc,
+ acc_en => tlb_plru_acc_en,
+ lru => tlb_plru_out
+ );
+
+ process(all)
+ begin
+ -- PLRU interface
+ if r1.tlb_hit_index = i then
+ tlb_plru_acc_en <= r1.tlb_hit;
+ else
+ tlb_plru_acc_en <= '0';
+ end if;
+ tlb_plru_acc <= std_ulogic_vector(to_unsigned(r1.tlb_hit_way, TLB_WAY_BITS));
+ tlb_plru_victim(i) <= tlb_plru_out;
+ end process;
+ end generate;
+ end generate;
+
+ tlb_search : process(all)
+ variable hitway : tlb_way_t;
+ variable hit : std_ulogic;
+ variable eatag : tlb_tag_t;
+ begin
+ tlb_req_index <= to_integer(unsigned(r0.req.addr(TLB_LG_PGSZ + TLB_SET_BITS - 1
+ downto TLB_LG_PGSZ)));
+ hitway := 0;
+ hit := '0';
+ eatag := r0.req.addr(63 downto TLB_LG_PGSZ + TLB_SET_BITS);
+ for i in tlb_way_t loop
+ if tlb_valid_way(i) = '1' and
+ read_tlb_tag(i, tlb_tag_way) = eatag then
+ hitway := i;
+ hit := '1';
+ end if;
+ end loop;
+ tlb_hit <= hit and r0_valid;
+ tlb_hit_way <= hitway;
+ if tlb_hit = '1' then
+ pte <= read_tlb_pte(hitway, tlb_pte_way);
+ else
+ pte <= (others => '0');
+ end if;
+ valid_ra <= tlb_hit or not r0.req.virt_mode;
+ if r0.req.virt_mode = '1' then
+ ra <= pte(REAL_ADDR_BITS - 1 downto TLB_LG_PGSZ) &
+ r0.req.addr(TLB_LG_PGSZ - 1 downto ROW_OFF_BITS) &
+ (ROW_OFF_BITS-1 downto 0 => '0');
+ perm_attr <= extract_perm_attr(pte);
+ else
+ ra <= r0.req.addr(REAL_ADDR_BITS - 1 downto ROW_OFF_BITS) &
+ (ROW_OFF_BITS-1 downto 0 => '0');
+ perm_attr <= real_mode_perm_attr;
+ end if;
+ end process;
+
+ tlb_update : process(clk)
+ variable tlbie : std_ulogic;
+ variable tlbwe : std_ulogic;
+ variable repl_way : tlb_way_t;
+ variable eatag : tlb_tag_t;
+ variable tagset : tlb_way_tags_t;
+ variable pteset : tlb_way_ptes_t;
+ begin
+ if rising_edge(clk) then
+ tlbie := r0_valid and r0.tlbie;
+ tlbwe := r0_valid and r0.tlbld;
+ if rst = '1' or (tlbie = '1' and r0.doall = '1') then
+ -- clear all valid bits at once
+ for i in tlb_index_t loop
+ dtlb_valids(i) <= (others => '0');
+ end loop;
+ elsif tlbie = '1' then
+ if tlb_hit = '1' then
+ dtlb_valids(tlb_req_index)(tlb_hit_way) <= '0';
+ end if;
+ elsif tlbwe = '1' then
+ if tlb_hit = '1' then
+ repl_way := tlb_hit_way;
+ else
+ repl_way := to_integer(unsigned(tlb_plru_victim(tlb_req_index)));
+ end if;
+ eatag := r0.req.addr(63 downto TLB_LG_PGSZ + TLB_SET_BITS);
+ tagset := tlb_tag_way;
+ write_tlb_tag(repl_way, tagset, eatag);
+ dtlb_tags(tlb_req_index) <= tagset;
+ pteset := tlb_pte_way;
+ write_tlb_pte(repl_way, pteset, r0.req.data);
+ dtlb_ptes(tlb_req_index) <= pteset;
+ dtlb_valids(tlb_req_index)(repl_way) <= '1';
+ end if;
+ end if;
+ end process;
+
-- Generate PLRUs
maybe_plrus: if NUM_WAYS > 1 generate
begin
lru => plru_out
);
- process(req_index, req_op, req_hit_way, plru_out)
+ process(all)
begin
-- PLRU interface
- if (req_op = OP_LOAD_HIT or
- req_op = OP_STORE_HIT) and req_index = i then
- plru_acc_en <= '1';
+ if r1.hit_index = i then
+ plru_acc_en <= r1.cache_hit;
else
plru_acc_en <= '0';
end if;
- plru_acc <= std_ulogic_vector(to_unsigned(req_hit_way, WAY_BITS));
+ plru_acc <= std_ulogic_vector(to_unsigned(r1.hit_way, WAY_BITS));
plru_victim(i) <= plru_out;
end process;
end generate;
end generate;
+ -- Cache tag RAM read port
+ cache_tag_read : process(clk)
+ variable index : index_t;
+ begin
+ if rising_edge(clk) then
+ if r0_stall = '1' then
+ index := req_index;
+ elsif m_in.valid = '1' then
+ index := get_index(m_in.addr);
+ else
+ index := get_index(d_in.addr);
+ end if;
+ cache_tag_set <= cache_tags(index);
+ end if;
+ end process;
+
-- Cache request parsing and hit detection
dcache_request : process(all)
- variable is_hit : std_ulogic;
- variable hit_way : way_t;
- variable op : op_t;
- variable tmp : std_ulogic_vector(63 downto 0);
- variable data : std_ulogic_vector(63 downto 0);
- variable opsel : std_ulogic_vector(3 downto 0);
+ variable is_hit : std_ulogic;
+ variable hit_way : way_t;
+ variable op : op_t;
+ variable opsel : std_ulogic_vector(2 downto 0);
+ variable go : std_ulogic;
+ variable nc : std_ulogic;
+ variable s_hit : std_ulogic;
+ variable s_tag : cache_tag_t;
+ variable s_pte : tlb_pte_t;
+ variable s_ra : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+ variable hit_set : std_ulogic_vector(TLB_NUM_WAYS - 1 downto 0);
+ variable hit_way_set : hit_way_set_t;
+ variable rel_matches : std_ulogic_vector(TLB_NUM_WAYS - 1 downto 0);
+ variable rel_match : std_ulogic;
begin
-- Extract line, row and tag from request
- req_index <= get_index(d_in.addr);
- req_row <= get_row(d_in.addr);
- req_tag <= get_tag(d_in.addr);
+ req_index <= get_index(r0.req.addr);
+ req_row <= get_row(r0.req.addr);
+ req_tag <= get_tag(ra);
- -- Calculate address of beginning of cache line, will be
- -- used for cache miss processing if needed
- --
- req_laddr <= d_in.addr(63 downto LINE_OFF_BITS) &
- (LINE_OFF_BITS-1 downto 0 => '0');
+ go := r0_valid and not (r0.tlbie or r0.tlbld) and not r1.ls_error;
-- Test if pending request is a hit on any way
- hit_way := 0;
- is_hit := '0';
- for i in way_t loop
- if d_in.valid = '1' and cache_valids(req_index)(i) = '1' then
- if read_tag(i, cache_tags(req_index)) = req_tag then
- hit_way := i;
- is_hit := '1';
- end if;
- end if;
- end loop;
+ -- In order to make timing in virtual mode, when we are using the TLB,
+ -- we compare each way with each of the real addresses from each way of
+ -- the TLB, and then decide later which match to use.
+ hit_way := 0;
+ is_hit := '0';
+ rel_match := '0';
+ if r0.req.virt_mode = '1' then
+ rel_matches := (others => '0');
+ for j in tlb_way_t loop
+ hit_way_set(j) := 0;
+ s_hit := '0';
+ s_pte := read_tlb_pte(j, tlb_pte_way);
+ s_ra := s_pte(REAL_ADDR_BITS - 1 downto TLB_LG_PGSZ) &
+ r0.req.addr(TLB_LG_PGSZ - 1 downto 0);
+ s_tag := get_tag(s_ra);
+ for i in way_t loop
+ if go = '1' and cache_valids(req_index)(i) = '1' and
+ read_tag(i, cache_tag_set) = s_tag and
+ tlb_valid_way(j) = '1' then
+ hit_way_set(j) := i;
+ s_hit := '1';
+ end if;
+ end loop;
+ hit_set(j) := s_hit;
+ if s_tag = r1.reload_tag then
+ rel_matches(j) := '1';
+ end if;
+ end loop;
+ if tlb_hit = '1' then
+ is_hit := hit_set(tlb_hit_way);
+ hit_way := hit_way_set(tlb_hit_way);
+ rel_match := rel_matches(tlb_hit_way);
+ end if;
+ else
+ s_tag := get_tag(r0.req.addr);
+ for i in way_t loop
+ if go = '1' and cache_valids(req_index)(i) = '1' and
+ read_tag(i, cache_tag_set) = s_tag then
+ hit_way := i;
+ is_hit := '1';
+ end if;
+ end loop;
+ if s_tag = r1.reload_tag then
+ rel_match := '1';
+ end if;
+ end if;
+ req_same_tag <= rel_match;
+
+ -- See if the request matches the line currently being reloaded
+ if r1.state = RELOAD_WAIT_ACK and req_index = r1.store_index and
+ rel_match = '1' then
+ -- For a store, consider this a hit even if the row isn't valid
+ -- since it will be by the time we perform the store.
+ -- For a load, check the appropriate row valid bit.
+ is_hit := not r0.req.load or r1.rows_valid(req_row mod ROW_PER_LINE);
+ hit_way := replace_way;
+ end if;
+
+ -- Whether to use forwarded data for a load or not
+ use_forward1_next <= '0';
+ if get_row(r1.req.real_addr) = req_row and r1.req.hit_way = hit_way then
+ -- Only need to consider r1.write_bram here, since if we are
+ -- writing refill data here, then we don't have a cache hit this
+ -- cycle on the line being refilled. (There is the possibility
+ -- that the load following the load miss that started the refill
+ -- could be to the old contents of the victim line, since it is a
+ -- couple of cycles after the refill starts before we see the
+ -- updated cache tag. In that case we don't use the bypass.)
+ use_forward1_next <= r1.write_bram;
+ end if;
+ use_forward2_next <= '0';
+ if r1.forward_row1 = req_row and r1.forward_way1 = hit_way then
+ use_forward2_next <= r1.forward_valid1;
+ end if;
-- The way that matched on a hit
req_hit_way <= hit_way;
- -- The way to replace on a miss
- replace_way <= to_integer(unsigned(plru_victim(req_index)));
-
- -- Combine the request and cache his status to decide what
+ -- The way to replace on a miss
+ if r1.write_tag = '1' then
+ replace_way <= to_integer(unsigned(plru_victim(r1.store_index)));
+ else
+ replace_way <= r1.store_way;
+ end if;
+
+ -- work out whether we have permission for this access
+ -- NB we don't yet implement AMR, thus no KUAP
+ rc_ok <= perm_attr.reference and (r0.req.load or perm_attr.changed);
+ perm_ok <= (r0.req.priv_mode or not perm_attr.priv) and
+ (perm_attr.wr_perm or (r0.req.load and perm_attr.rd_perm));
+ access_ok <= valid_ra and perm_ok and rc_ok;
+
+ -- Combine the request and cache hit status to decide what
-- operation needs to be done
--
- opsel := d_in.valid & d_in.load & d_in.nc & is_hit;
- case opsel is
- when "1101" => op := OP_LOAD_HIT;
- when "1100" => op := OP_LOAD_MISS;
- when "1110" => op := OP_LOAD_NC;
- when "1001" => op := OP_STORE_HIT;
- when "1000" => op := OP_STORE_MISS;
- when "1010" => op := OP_STORE_MISS;
- when "1011" => op := OP_BAD;
- when "1111" => op := OP_BAD;
- when others => op := OP_NONE;
- end case;
-
+ nc := r0.req.nc or perm_attr.nocache;
+ op := OP_NONE;
+ if go = '1' then
+ if access_ok = '0' then
+ op := OP_BAD;
+ elsif cancel_store = '1' then
+ op := OP_STCX_FAIL;
+ else
+ opsel := r0.req.load & nc & is_hit;
+ case opsel is
+ when "101" => op := OP_LOAD_HIT;
+ when "100" => op := OP_LOAD_MISS;
+ when "110" => op := OP_LOAD_NC;
+ when "001" => op := OP_STORE_HIT;
+ when "000" => op := OP_STORE_MISS;
+ when "010" => op := OP_STORE_MISS;
+ when "011" => op := OP_BAD;
+ when "111" => op := OP_BAD;
+ when others => op := OP_NONE;
+ end case;
+ end if;
+ end if;
req_op <= op;
-
+ req_go <= go;
+
+ -- Version of the row number that is valid one cycle earlier
+ -- in the cases where we need to read the cache data BRAM.
+ -- If we're stalling then we need to keep reading the last
+ -- row requested.
+ if r0_stall = '0' then
+ if m_in.valid = '1' then
+ early_req_row <= get_row(m_in.addr);
+ else
+ early_req_row <= get_row(d_in.addr);
+ end if;
+ else
+ early_req_row <= req_row;
+ end if;
end process;
- --
- -- Misc signal assignments
- --
-
-- Wire up wishbone request latch out of stage 1
wishbone_out <= r1.wb;
- -- Wishbone & BRAM write data formatting for stores (most of it already
- -- happens in loadstore1, this is the remaining data shifting)
- --
- store_data <= std_logic_vector(shift_left(unsigned(d_in.data),
- wishbone_data_shift(d_in.addr)));
-
- -- Wishbone read and write and BRAM write sel bits generation
- bus_sel <= wishbone_data_sel(d_in.length, d_in.addr);
-
- -- TODO: Generate errors
- -- err_nc_collision <= '1' when req_op = OP_BAD else '0';
+ -- Handle load-with-reservation and store-conditional instructions
+ reservation_comb: process(all)
+ begin
+ cancel_store <= '0';
+ set_rsrv <= '0';
+ clear_rsrv <= '0';
+ if r0_valid = '1' and r0.req.reserve = '1' then
+ -- XXX generate alignment interrupt if address is not aligned
+ -- XXX or if r0.req.nc = '1'
+ if r0.req.load = '1' then
+ -- load with reservation
+ set_rsrv <= r0.req.atomic_last;
+ else
+ -- store conditional
+ clear_rsrv <= r0.req.atomic_last;
+ if reservation.valid = '0' or
+ r0.req.addr(63 downto LINE_OFF_BITS) /= reservation.addr then
+ cancel_store <= '1';
+ end if;
+ end if;
+ end if;
+ end process;
- -- Generate stalls from stage 1 state machine
- stall_out <= '1' when r1.state /= IDLE else '0';
+ reservation_reg: process(clk)
+ begin
+ if rising_edge(clk) then
+ if rst = '1' then
+ reservation.valid <= '0';
+ elsif r0_valid = '1' and access_ok = '1' then
+ if clear_rsrv = '1' then
+ reservation.valid <= '0';
+ elsif set_rsrv = '1' then
+ reservation.valid <= '1';
+ reservation.addr <= r0.req.addr(63 downto LINE_OFF_BITS);
+ end if;
+ end if;
+ end if;
+ end process;
- -- Writeback (loads and reg updates) & completion control logic
+ -- Return data for loads & completion control logic
--
writeback_control: process(all)
+ variable data_out : std_ulogic_vector(63 downto 0);
+ variable data_fwd : std_ulogic_vector(63 downto 0);
+ variable j : integer;
begin
-
- -- The mux on d_out.write reg defaults to the normal load hit case.
- d_out.write_enable <= '0';
- d_out.valid <= '0';
- d_out.write_reg <= r2.load_reg;
- d_out.write_data <= cache_out(r2.hit_way);
- d_out.write_len <= r2.length;
- d_out.write_shift <= r2.data_shift;
- d_out.sign_extend <= r2.sign_extend;
- d_out.byte_reverse <= r2.byte_reverse;
- d_out.second_word <= '0';
- d_out.xerc <= r2.xerc;
+ -- Use the bypass if are reading the row that was written 1 or 2 cycles
+ -- ago, including for the slow_valid = 1 case (i.e. completing a load
+ -- miss or a non-cacheable load).
+ if r1.use_forward1 = '1' then
+ data_fwd := r1.forward_data1;
+ else
+ data_fwd := r1.forward_data2;
+ end if;
+ data_out := cache_out(r1.hit_way);
+ for i in 0 to 7 loop
+ j := i * 8;
+ if r1.forward_sel(i) = '1' then
+ data_out(j + 7 downto j) := data_fwd(j + 7 downto j);
+ end if;
+ end loop;
+
+ d_out.valid <= r1.ls_valid;
+ d_out.data <= data_out;
+ d_out.store_done <= not r1.stcx_fail;
+ d_out.error <= r1.ls_error;
+ d_out.cache_paradox <= r1.cache_paradox;
+
+ -- Outputs to MMU
+ m_out.done <= r1.mmu_done;
+ m_out.err <= r1.mmu_error;
+ m_out.data <= data_out;
-- We have a valid load or store hit or we just completed a slow
-- op such as a load miss, a NC load or a store
--
-- Sanity: Only one of these must be set in any given cycle
- assert (r1.update_valid and r2.hit_load_valid) /= '1' report
- "unexpected hit_load_delayed collision with update_valid"
+ assert (r1.slow_valid and r1.stcx_fail) /= '1' report
+ "unexpected slow_valid collision with stcx_fail"
severity FAILURE;
- assert (r1.slow_valid and r2.hit_load_valid) /= '1' report
+ assert ((r1.slow_valid or r1.stcx_fail) and r1.hit_load_valid) /= '1' report
"unexpected hit_load_delayed collision with slow_valid"
severity FAILURE;
- assert (r1.slow_valid and r1.update_valid) /= '1' report
- "unexpected update_valid collision with slow_valid"
- severity FAILURE;
-
- -- Delayed load hit case is the standard path
- if r2.hit_load_valid = '1' then
- d_out.write_enable <= '1';
-
- -- If it's not a load with update, complete it now
- if r2.load_is_update = '0' then
- d_out.valid <= '1';
- end if;
- end if;
- -- Slow ops (load miss, NC, stores)
- if r1.slow_valid = '1' then
- -- If it's a load, enable register writeback and switch
- -- mux accordingly
- --
- if r1.req.load then
- d_out.write_reg <= r1.req.write_reg;
- d_out.write_enable <= '1';
-
- -- Read data comes from the slow data latch, formatter
- -- from the latched request.
- --
- d_out.write_data <= r1.slow_data;
- d_out.write_shift <= r1.req.addr(2 downto 0);
- d_out.sign_extend <= r1.req.sign_extend;
- d_out.byte_reverse <= r1.req.byte_reverse;
- d_out.write_len <= r1.req.length;
- d_out.xerc <= r1.req.xerc;
- end if;
-
- -- If it's a store or a non-update load form, complete now
- if r1.req.load = '0' or r1.req.update = '0' then
- d_out.valid <= '1';
- end if;
- end if;
-
- -- We have a register update to do.
- if r1.update_valid = '1' then
- d_out.write_enable <= '1';
- d_out.write_reg <= r1.req.update_reg;
-
- -- Change the read data mux to the address that's going into
- -- the register and the formatter does nothing.
- --
- d_out.write_data <= r1.req.addr;
- d_out.write_shift <= "000";
- d_out.write_len <= "1000";
- d_out.sign_extend <= '0';
- d_out.byte_reverse <= '0';
- d_out.xerc <= r1.req.xerc;
-
- -- If it was a load, this completes the operation (load with
- -- update case).
- --
- if r1.req.load = '1' then
- d_out.valid <= '1';
- end if;
- end if;
+ if r1.mmu_req = '0' then
+ -- Request came from loadstore1...
+ -- Load hit case is the standard path
+ if r1.hit_load_valid = '1' then
+ report "completing load hit data=" & to_hstring(data_out);
+ end if;
+
+ -- error cases complete without stalling
+ if r1.ls_error = '1' then
+ report "completing ld/st with error";
+ end if;
+
+ -- Slow ops (load miss, NC, stores)
+ if r1.slow_valid = '1' then
+ report "completing store or load miss data=" & to_hstring(data_out);
+ end if;
+
+ else
+ -- Request came from MMU
+ if r1.hit_load_valid = '1' then
+ report "completing load hit to MMU, data=" & to_hstring(m_out.data);
+ end if;
+
+ -- error cases complete without stalling
+ if r1.mmu_error = '1' then
+ report "completing MMU ld with error";
+ end if;
+
+ -- Slow ops (i.e. load miss)
+ if r1.slow_valid = '1' then
+ report "completing MMU load miss, data=" & to_hstring(m_out.data);
+ end if;
+ end if;
end process;
signal wr_addr : std_ulogic_vector(ROW_BITS-1 downto 0);
signal wr_data : std_ulogic_vector(wishbone_data_bits-1 downto 0);
signal wr_sel : std_ulogic_vector(ROW_SIZE-1 downto 0);
+ signal wr_sel_m : std_ulogic_vector(ROW_SIZE-1 downto 0);
signal dout : cache_row_t;
begin
way: entity work.cache_ram
rd_en => do_read,
rd_addr => rd_addr,
rd_data => dout,
- wr_en => do_write,
- wr_sel => wr_sel,
+ wr_sel => wr_sel_m,
wr_addr => wr_addr,
wr_data => wr_data
);
process(all)
- variable tmp_adr : std_ulogic_vector(63 downto 0);
- variable reloading : boolean;
begin
-- Cache hit reads
do_read <= '1';
- rd_addr <= std_ulogic_vector(to_unsigned(req_row, ROW_BITS));
+ rd_addr <= std_ulogic_vector(to_unsigned(early_req_row, ROW_BITS));
cache_out(i) <= dout;
-- Write mux:
-- Defaults to wishbone read responses (cache refill),
--
-- For timing, the mux on wr_data/sel/addr is not dependent on anything
- -- other than the current state. Only the do_write signal is.
+ -- other than the current state.
--
- if r1.state = IDLE then
- -- When IDLE, the only write path is the store-hit update case
- wr_addr <= std_ulogic_vector(to_unsigned(req_row, ROW_BITS));
- wr_data <= store_data;
- wr_sel <= bus_sel;
- else
- -- Otherwise, we might be doing a reload
- wr_data <= wishbone_in.dat;
- wr_sel <= (others => '1');
- wr_addr <= std_ulogic_vector(to_unsigned(r1.store_row, ROW_BITS));
- end if;
+ wr_sel_m <= (others => '0');
- -- The two actual write cases here
do_write <= '0';
- reloading := r1.state = RELOAD_WAIT_ACK;
- if reloading and wishbone_in.ack = '1' and r1.store_way = i then
- do_write <= '1';
- end if;
- if req_op = OP_STORE_HIT and req_hit_way = i then
- assert not reloading report "Store hit while in state:" &
- state_t'image(r1.state)
- severity FAILURE;
- do_write <= '1';
+ if r1.write_bram = '1' then
+ -- Write store data to BRAM. This happens one cycle after the
+ -- store is in r0.
+ wr_data <= r1.req.data;
+ wr_sel <= r1.req.byte_sel;
+ wr_addr <= std_ulogic_vector(to_unsigned(get_row(r1.req.real_addr), ROW_BITS));
+ if i = r1.req.hit_way then
+ do_write <= '1';
+ end if;
+ else
+ -- Otherwise, we might be doing a reload or a DCBZ
+ if r1.dcbz = '1' then
+ wr_data <= (others => '0');
+ else
+ wr_data <= wishbone_in.dat;
+ end if;
+ wr_addr <= std_ulogic_vector(to_unsigned(r1.store_row, ROW_BITS));
+ wr_sel <= (others => '1');
+
+ if r1.state = RELOAD_WAIT_ACK and wishbone_in.ack = '1' and replace_way = i then
+ do_write <= '1';
+ end if;
end if;
- end process;
+
+ -- Mask write selects with do_write since BRAM doesn't
+ -- have a global write-enable
+ if do_write = '1' then
+ wr_sel_m <= wr_sel;
+ end if;
+
+ end process;
end generate;
--
- -- Cache hit synchronous machine for the easy case. This handles
- -- non-update form load hits and stage 1 to stage 2 transfers
+ -- Cache hit synchronous machine for the easy case. This handles load hits.
+ -- It also handles error cases (TLB miss, cache paradox)
--
dcache_fast_hit : process(clk)
begin
if rising_edge(clk) then
- -- stage 1 -> stage 2
- r2.hit_load_valid <= r1.hit_load_valid;
- r2.hit_way <= r1.hit_way;
- r2.load_is_update <= r1.req.update;
- r2.load_reg <= r1.req.write_reg;
- r2.data_shift <= r1.req.addr(2 downto 0);
- r2.length <= r1.req.length;
- r2.sign_extend <= r1.req.sign_extend;
- r2.byte_reverse <= r1.req.byte_reverse;
-
- -- If we have a request incoming, we have to latch it as d_in.valid
- -- is only set for a single cycle. It's up to the control logic to
- -- ensure we don't override an uncompleted request (for now we are
- -- single issue on load/stores so we are fine, later, we can generate
- -- a stall output if necessary).
-
- if req_op /= OP_NONE then
- r1.req <= d_in;
-
+ if req_op /= OP_NONE then
report "op:" & op_t'image(req_op) &
- " addr:" & to_hstring(d_in.addr) &
- " upd:" & std_ulogic'image(d_in.update) &
- " nc:" & std_ulogic'image(d_in.nc) &
- " reg:" & to_hstring(d_in.write_reg) &
+ " addr:" & to_hstring(r0.req.addr) &
+ " nc:" & std_ulogic'image(r0.req.nc) &
" idx:" & integer'image(req_index) &
" tag:" & to_hstring(req_tag) &
" way: " & integer'image(req_hit_way);
end if;
+ if r0_valid = '1' then
+ r1.mmu_req <= r0.mmu_req;
+ end if;
- -- Fast path for load/store hits. Set signals for the writeback controls.
+ -- Fast path for load/store hits. Set signals for the writeback controls.
+ r1.hit_way <= req_hit_way;
+ r1.hit_index <= req_index;
if req_op = OP_LOAD_HIT then
- r1.hit_way <= req_hit_way;
r1.hit_load_valid <= '1';
else
r1.hit_load_valid <= '0';
end if;
+ if req_op = OP_LOAD_HIT or req_op = OP_STORE_HIT then
+ r1.cache_hit <= '1';
+ else
+ r1.cache_hit <= '0';
+ end if;
+
+ if req_op = OP_BAD then
+ report "Signalling ld/st error valid_ra=" & std_ulogic'image(valid_ra) &
+ " rc_ok=" & std_ulogic'image(rc_ok) & " perm_ok=" & std_ulogic'image(perm_ok);
+ r1.ls_error <= not r0.mmu_req;
+ r1.mmu_error <= r0.mmu_req;
+ r1.cache_paradox <= access_ok;
+ else
+ r1.ls_error <= '0';
+ r1.mmu_error <= '0';
+ r1.cache_paradox <= '0';
+ end if;
+
+ if req_op = OP_STCX_FAIL then
+ r1.stcx_fail <= '1';
+ else
+ r1.stcx_fail <= '0';
+ end if;
+
+ -- Record TLB hit information for updating TLB PLRU
+ r1.tlb_hit <= tlb_hit;
+ r1.tlb_hit_way <= tlb_hit_way;
+ r1.tlb_hit_index <= tlb_req_index;
+
end if;
end process;
--
- -- Every other case is handled by this stage machine:
+ -- Memory accesses are handled by this state machine:
--
-- * Cache load miss/reload (in conjunction with "rams")
- -- * Load hits for update forms
-- * Load hits for non-cachable forms
-- * Stores (the collision case is handled in "rams")
--
-- operates at stage 1.
--
dcache_slow : process(clk)
- variable tagset : cache_tags_set_t;
variable stbs_done : boolean;
+ variable req : mem_access_request_t;
+ variable acks : unsigned(2 downto 0);
begin
if rising_edge(clk) then
+ r1.use_forward1 <= use_forward1_next;
+ r1.forward_sel <= (others => '0');
+ if use_forward1_next = '1' then
+ r1.forward_sel <= r1.req.byte_sel;
+ elsif use_forward2_next = '1' then
+ r1.forward_sel <= r1.forward_sel1;
+ end if;
+
+ r1.forward_data2 <= r1.forward_data1;
+ if r1.write_bram = '1' then
+ r1.forward_data1 <= r1.req.data;
+ r1.forward_sel1 <= r1.req.byte_sel;
+ r1.forward_way1 <= r1.req.hit_way;
+ r1.forward_row1 <= get_row(r1.req.real_addr);
+ r1.forward_valid1 <= '1';
+ else
+ if r1.dcbz = '1' then
+ r1.forward_data1 <= (others => '0');
+ else
+ r1.forward_data1 <= wishbone_in.dat;
+ end if;
+ r1.forward_sel1 <= (others => '1');
+ r1.forward_way1 <= replace_way;
+ r1.forward_row1 <= r1.store_row;
+ r1.forward_valid1 <= '0';
+ end if;
+
-- On reset, clear all valid bits to force misses
if rst = '1' then
for i in index_t loop
cache_valids(i) <= (others => '0');
end loop;
r1.state <= IDLE;
+ r1.full <= '0';
r1.slow_valid <= '0';
- r1.update_valid <= '0';
r1.wb.cyc <= '0';
r1.wb.stb <= '0';
+ r1.ls_valid <= '0';
+ r1.mmu_done <= '0';
-- Not useful normally but helps avoiding tons of sim warnings
r1.wb.adr <= (others => '0');
else
-- One cycle pulses reset
r1.slow_valid <= '0';
- r1.update_valid <= '0';
-
- -- We cannot currently process a new request when not idle
- assert req_op = OP_NONE or r1.state = IDLE report "request " &
- op_t'image(req_op) & " while in state " & state_t'image(r1.state)
- severity FAILURE;
+ r1.write_bram <= '0';
+ r1.inc_acks <= '0';
+ r1.dec_acks <= '0';
+
+ r1.ls_valid <= '0';
+ -- complete tlbies and TLB loads in the third cycle
+ r1.mmu_done <= r0_valid and (r0.tlbie or r0.tlbld);
+ if req_op = OP_LOAD_HIT or req_op = OP_STCX_FAIL then
+ if r0.mmu_req = '0' then
+ r1.ls_valid <= '1';
+ else
+ r1.mmu_done <= '1';
+ end if;
+ end if;
+
+ if r1.write_tag = '1' then
+ -- Store new tag in selected way
+ for i in 0 to NUM_WAYS-1 loop
+ if i = replace_way then
+ cache_tags(r1.store_index)((i + 1) * TAG_WIDTH - 1 downto i * TAG_WIDTH) <=
+ (TAG_WIDTH - 1 downto TAG_BITS => '0') & r1.reload_tag;
+ end if;
+ end loop;
+ r1.store_way <= replace_way;
+ r1.write_tag <= '0';
+ end if;
+
+ -- Take request from r1.req if there is one there,
+ -- else from req_op, ra, etc.
+ if r1.full = '1' then
+ req := r1.req;
+ else
+ req.op := req_op;
+ req.valid := req_go;
+ req.mmu_req := r0.mmu_req;
+ req.dcbz := r0.req.dcbz;
+ req.real_addr := ra;
+ -- Force data to 0 for dcbz
+ if r0.req.dcbz = '1' then
+ req.data := (others => '0');
+ elsif r0.d_valid = '1' then
+ req.data := r0.req.data;
+ else
+ req.data := d_in.data;
+ end if;
+ -- Select all bytes for dcbz and for cacheable loads
+ if r0.req.dcbz = '1' or (r0.req.load = '1' and r0.req.nc = '0') then
+ req.byte_sel := (others => '1');
+ else
+ req.byte_sel := r0.req.byte_sel;
+ end if;
+ req.hit_way := req_hit_way;
+ req.same_tag := req_same_tag;
+
+ -- Store the incoming request from r0, if it is a slow request
+ -- Note that r1.full = 1 implies req_op = OP_NONE
+ if req_op = OP_LOAD_MISS or req_op = OP_LOAD_NC or
+ req_op = OP_STORE_MISS or req_op = OP_STORE_HIT then
+ r1.req <= req;
+ r1.full <= '1';
+ end if;
+ end if;
-- Main state machine
case r1.state is
- when IDLE =>
- case req_op is
- when OP_LOAD_HIT =>
- -- We have a load with update hit, we need the delayed update cycle
- if d_in.update = '1' then
- r1.state <= LOAD_UPDATE;
- end if;
-
- when OP_LOAD_MISS =>
+ when IDLE =>
+ r1.wb.adr <= req.real_addr(r1.wb.adr'left downto 0);
+ r1.wb.sel <= req.byte_sel;
+ r1.wb.dat <= req.data;
+ r1.dcbz <= req.dcbz;
+
+ -- Keep track of our index and way for subsequent stores.
+ r1.store_index <= get_index(req.real_addr);
+ r1.store_row <= get_row(req.real_addr);
+ r1.end_row_ix <= get_row_of_line(get_row(req.real_addr)) - 1;
+ r1.reload_tag <= get_tag(req.real_addr);
+ r1.req.same_tag <= '1';
+
+ if req.op = OP_STORE_HIT then
+ r1.store_way <= req.hit_way;
+ end if;
+
+ -- Reset per-row valid bits, ready for handling OP_LOAD_MISS
+ for i in 0 to ROW_PER_LINE - 1 loop
+ r1.rows_valid(i) <= '0';
+ end loop;
+
+ case req.op is
+ when OP_LOAD_HIT =>
+ -- stay in IDLE state
+
+ when OP_LOAD_MISS =>
-- Normal load cache miss, start the reload machine
--
- report "cache miss addr:" & to_hstring(d_in.addr) &
- " idx:" & integer'image(req_index) &
- " way:" & integer'image(replace_way) &
- " tag:" & to_hstring(req_tag);
-
- -- Force misses on that way while reloading that line
- cache_valids(req_index)(replace_way) <= '0';
-
- -- Store new tag in selected way
- for i in 0 to NUM_WAYS-1 loop
- if i = replace_way then
- tagset := cache_tags(req_index);
- write_tag(i, tagset, req_tag);
- cache_tags(req_index) <= tagset;
- end if;
- end loop;
-
- -- Keep track of our index and way for subsequent stores.
- r1.store_index <= req_index;
- r1.store_way <= replace_way;
- r1.store_row <= get_row(req_laddr);
-
- -- Prep for first wishbone read. We calculate the address of
- -- the start of the cache line and start the WB cycle
- --
- r1.wb.adr <= req_laddr(r1.wb.adr'left downto 0);
- r1.wb.sel <= (others => '1');
+ report "cache miss real addr:" & to_hstring(req.real_addr) &
+ " idx:" & integer'image(get_index(req.real_addr)) &
+ " tag:" & to_hstring(get_tag(req.real_addr));
+
+ -- Start the wishbone cycle
r1.wb.we <= '0';
r1.wb.cyc <= '1';
r1.wb.stb <= '1';
-- Track that we had one request sent
r1.state <= RELOAD_WAIT_ACK;
+ r1.write_tag <= '1';
when OP_LOAD_NC =>
- r1.wb.sel <= bus_sel;
- r1.wb.adr <= d_in.addr(r1.wb.adr'left downto 3) & "000";
r1.wb.cyc <= '1';
r1.wb.stb <= '1';
r1.wb.we <= '0';
r1.state <= NC_LOAD_WAIT_ACK;
- when OP_STORE_HIT | OP_STORE_MISS =>
- -- For store-with-update do the register update
- if d_in.update = '1' then
- r1.update_valid <= '1';
- end if;
- r1.wb.sel <= bus_sel;
- r1.wb.adr <= d_in.addr(r1.wb.adr'left downto 3) & "000";
- r1.wb.dat <= store_data;
+ when OP_STORE_HIT | OP_STORE_MISS =>
+ if req.dcbz = '0' then
+ r1.state <= STORE_WAIT_ACK;
+ r1.acks_pending <= to_unsigned(1, 3);
+ r1.full <= '0';
+ r1.slow_valid <= '1';
+ if req.mmu_req = '0' then
+ r1.ls_valid <= '1';
+ else
+ r1.mmu_done <= '1';
+ end if;
+ if req.op = OP_STORE_HIT then
+ r1.write_bram <= '1';
+ end if;
+ else
+ -- dcbz is handled much like a load miss except
+ -- that we are writing to memory instead of reading
+ r1.state <= RELOAD_WAIT_ACK;
+ if req.op = OP_STORE_MISS then
+ r1.write_tag <= '1';
+ end if;
+ end if;
+ r1.wb.we <= '1';
r1.wb.cyc <= '1';
r1.wb.stb <= '1';
- r1.wb.we <= '1';
- r1.state <= STORE_WAIT_ACK;
-- OP_NONE and OP_BAD do nothing
+ -- OP_BAD & OP_STCX_FAIL were handled above already
when OP_NONE =>
- when OP_BAD =>
+ when OP_BAD =>
+ when OP_STCX_FAIL =>
end case;
- when RELOAD_WAIT_ACK =>
- -- Requests are all sent if stb is 0
+ when RELOAD_WAIT_ACK =>
+ -- Requests are all sent if stb is 0
stbs_done := r1.wb.stb = '0';
-- If we are still sending requests, was one accepted ?
-- stb and set stbs_done so we can handle an eventual last
-- ack on the same cycle.
--
- if is_last_row_addr(r1.wb.adr) then
+ if is_last_row_addr(r1.wb.adr, r1.end_row_ix) then
r1.wb.stb <= '0';
stbs_done := true;
end if;
end if;
-- Incoming acks processing
+ r1.forward_valid1 <= wishbone_in.ack;
if wishbone_in.ack = '1' then
- -- Is this the data we were looking for ? Latch it so
- -- we can respond later. We don't currently complete the
- -- pending miss request immediately, we wait for the
- -- whole line to be loaded. The reason is that if we
- -- did, we would potentially get new requests in while
- -- not idle, which we don't currently know how to deal
- -- with.
- --
- if r1.store_row = get_row(r1.req.addr) then
- r1.slow_data <= wishbone_in.dat;
+ r1.rows_valid(r1.store_row mod ROW_PER_LINE) <= '1';
+ -- If this is the data we were looking for, we can
+ -- complete the request next cycle.
+ -- Compare the whole address in case the request in
+ -- r1.req is not the one that started this refill.
+ if req.valid = '1' and req.same_tag = '1' and
+ ((r1.dcbz = '1' and req.dcbz = '1') or
+ (r1.dcbz = '0' and req.op = OP_LOAD_MISS)) and
+ r1.store_row = get_row(req.real_addr) then
+ r1.full <= '0';
+ r1.slow_valid <= '1';
+ if r1.mmu_req = '0' then
+ r1.ls_valid <= '1';
+ else
+ r1.mmu_done <= '1';
+ end if;
+ r1.forward_sel <= (others => '1');
+ r1.use_forward1 <= '1';
end if;
-- Check for completion
- if stbs_done and is_last_row(r1.store_row) then
+ if stbs_done and is_last_row(r1.store_row, r1.end_row_ix) then
-- Complete wishbone cycle
r1.wb.cyc <= '0';
-- Cache line is now valid
cache_valids(r1.store_index)(r1.store_way) <= '1';
- -- Complete the load that missed. For load with update
- -- we also need to do the deferred update cycle.
- --
- r1.slow_valid <= '1';
- if r1.req.load = '1' and r1.req.update = '1' then
- r1.state <= LOAD_UPDATE;
- report "completing miss with load-update !";
- else
- r1.state <= IDLE;
- report "completing miss !";
- end if;
+ r1.state <= IDLE;
end if;
-- Increment store row counter
r1.store_row <= next_row(r1.store_row);
end if;
- when LOAD_UPDATE =>
- -- We need the extra cycle to complete a load with update
- r1.state <= LOAD_UPDATE2;
- when LOAD_UPDATE2 =>
- -- We need the extra cycle to complete a load with update
- r1.update_valid <= '1';
- r1.state <= IDLE;
+ when STORE_WAIT_ACK =>
+ stbs_done := r1.wb.stb = '0';
+ acks := r1.acks_pending;
+ if r1.inc_acks /= r1.dec_acks then
+ if r1.inc_acks = '1' then
+ acks := acks + 1;
+ else
+ acks := acks - 1;
+ end if;
+ end if;
+ r1.acks_pending <= acks;
+ -- Clear stb when slave accepted request
+ if wishbone_in.stall = '0' then
+ -- See if there is another store waiting to be done
+ -- which is in the same real page.
+ if req.valid = '1' then
+ r1.wb.adr(SET_SIZE_BITS - 1 downto 0) <=
+ req.real_addr(SET_SIZE_BITS - 1 downto 0);
+ r1.wb.dat <= req.data;
+ r1.wb.sel <= req.byte_sel;
+ end if;
+ if acks < 7 and req.same_tag = '1' and
+ (req.op = OP_STORE_MISS or req.op = OP_STORE_HIT) then
+ r1.wb.stb <= '1';
+ stbs_done := false;
+ if req.op = OP_STORE_HIT then
+ r1.write_bram <= '1';
+ end if;
+ r1.full <= '0';
+ r1.slow_valid <= '1';
+ -- Store requests never come from the MMU
+ r1.ls_valid <= '1';
+ stbs_done := false;
+ r1.inc_acks <= '1';
+ else
+ r1.wb.stb <= '0';
+ stbs_done := true;
+ end if;
+ end if;
+
+ -- Got ack ? See if complete.
+ if wishbone_in.ack = '1' then
+ if stbs_done and acks = 1 then
+ r1.state <= IDLE;
+ r1.wb.cyc <= '0';
+ r1.wb.stb <= '0';
+ end if;
+ r1.dec_acks <= '1';
+ end if;
- when STORE_WAIT_ACK | NC_LOAD_WAIT_ACK =>
+ when NC_LOAD_WAIT_ACK =>
-- Clear stb when slave accepted request
if wishbone_in.stall = '0' then
r1.wb.stb <= '0';
-- Got ack ? complete.
if wishbone_in.ack = '1' then
- if r1.state = NC_LOAD_WAIT_ACK then
- r1.slow_data <= wishbone_in.dat;
- end if;
+ r1.state <= IDLE;
+ r1.full <= '0';
r1.slow_valid <= '1';
+ if r1.mmu_req = '0' then
+ r1.ls_valid <= '1';
+ else
+ r1.mmu_done <= '1';
+ end if;
+ r1.forward_sel <= (others => '1');
+ r1.use_forward1 <= '1';
r1.wb.cyc <= '0';
r1.wb.stb <= '0';
- r1.state <= IDLE;
end if;
- end case;
+ end case;
end if;
end if;
end process;
+
+ dc_log: if LOG_LENGTH > 0 generate
+ signal log_data : std_ulogic_vector(19 downto 0);
+ begin
+ dcache_log: process(clk)
+ begin
+ if rising_edge(clk) then
+ log_data <= r1.wb.adr(5 downto 3) &
+ wishbone_in.stall &
+ wishbone_in.ack &
+ r1.wb.stb & r1.wb.cyc &
+ d_out.error &
+ d_out.valid &
+ std_ulogic_vector(to_unsigned(op_t'pos(req_op), 3)) &
+ stall_out &
+ std_ulogic_vector(to_unsigned(tlb_hit_way, 3)) &
+ valid_ra &
+ std_ulogic_vector(to_unsigned(state_t'pos(r1.state), 3));
+ end if;
+ end process;
+ log_out <= log_data;
+ end generate;
end;
projects / microwatt.git / blobdiff